What is the correct name for state explosion from sensor discretization?
I would refer to your problem as having a continuous state space.
By using a 32-bit float variable you discritize it. However, creating states for every possible value of a 32-bit float variable is probably too much. You should decide on:


the variable range: what is the real range of the position variables (e.g. from 0 m to 10 m), 
and what is the resolution you require for your problem (e.g. 0.01 m or 0.1 m). 


Note that you should take into account: 


the sensor range resolution,
the required range and resolution for the problem.


Then, based on the number of states you could decide to discretize the states or to use a Monte Carlo approach. 

See for example the work of Brechtel et al. (2013).